The point is that I have seen in this web http://greenpassivesolar.com that there is a technical solution for the box size. She is using Magazine Basic theme. I asked the author of this magazine (Keya) and she has kindly shared with me how she solved it

I created a developer account with facebook and inserted an iframe. I then specified the dimensions of the iframe, such that it is 160px in width and 487px in height. I didn't use a plugin. The code can be seen with firebug, but I'll also insert it below:

That code only will work until Facebook notices it and updates their code to implement the minimum width in the iframe (or discontinues support for the iframe method entirely, which honestly would not surprise me).

I won't implement any workarounds or anything unsupported like this in SFC. Sorry. Feel free to use her approach instead.